Microwave coupling device



Dec. 2, 1947. I H. KIHN 2,431,941

MICROWAVE COUPLING DEVICE Filed Nov. 29, 1945 2 Sheets-Sheet 1 I I I f f h. 'M 'I I j 49 I; z if g 3 a v I WA Dec. 2, 1947.

H. KIHN 2,431,941

MICROWAVE COUPLING DEVICE Filed NOV. 29, 1943 2 Sheets-Sheet 2 Patented Dec. 2, 1947 Harry Kihn; Lawrenc Radio Corporationof Delaware eville, 'N.""J.', assignor "to of America," a corporation Application November 29, 194a serial Nc;i512,12i 6 Claims. (or. its-=44) This invention "relates" generally to microwave apparatus and more particularly to adjustable coupling devices for varying the transfer of microwaveenergyfrom' a microwave source toa waveguide transmission system. v 'Various types of microwave coupling devices have been employed heretofore in waveguide transmission"systems. One of the essential requirements for such devices'is that'the adjustment'of the transferred energy be gradual and readilyobtainableby means of simple operating mechanisms; "Another requirement of such devices is that electrical contact between movable conductive elements be accomplished at points of minimum microwave current distribution in order to minimize'imperfectcontact effects. A further requirement of such devices isthat they be extremely compact; since the physicalsizes of the circuit components "are' extremely critical at the super-high frequencies employed. first embodiment of the instantin'v'ention comprises a simple" mechanical structure for varying the microwave coupling b'etween'a microwave generator-such asgforexample; a Shepard tube cavity resonator deviceyand a waveguide transmission system which may be employed for trans mittingmicrowaveenergytoany selected type of load device. Shepard tubes include a short '00- axial transmission line, one end'of which terminatesin an output coupling loop within'the cavity resonator and the other end of which has a quarter wavelengthof the inner conductor ex-- posedfor coupling'to the load system. If desired the inner conductor may be exposed for one-half wavelength and terminated in a coupling lo'op connected to thecableouter conductor. The Shepard-tube is inserted in a standard wafertype octal socket which is secured to a platform which may be adjusted-vertically by-means of a simple rackand pinion adjusting mechanism.

.A constricted short length of round waveguide, having a cut-off frequency below the operating microwave-frequency, surrounds an aperture in oneof the facesof the rectangular waveguide transmission system, and includes cylindrical flexible contacts-which grasp the outer conductor ofthe short coaxialcable at any desired point above the-aperture in the rectangular waveguide face. This arrangement effectively minimizes leakage from-the rectangular waveguide, and provides electrical contact to the outer conductor of the coaxial cable. The depth to which the exposed quarter wavelength of the inner conductor of-thecoaxialcable penetrates the constricted small-round waveguide and the rectangular wave- "2 guide transmissionsystem may be-adjustedbythe rack and pinion mechanism to provide desired microwave coupling between the Shepard tube enerat or and the rectangular waveguide transmission-system.

A'notherarrangement which provides similar adjustment [or microwave coupling, employs a thumb 'screwmechanism which permits adjustment-of "the elevation-i of the Shepard tube with respect t o the rectangular transmission system hence adjustment-of the penetration of the Shepardftube output coaxial line into the con: striated circularwaveguide and the rectangular waveguide transmission system. If desired, the "short constricted 7 circular waveguide may be omitted, providing the aperture'in the rectangularwaveguide faces issufiiciently small to prevent sri'oiis leakage of microwave energy. The thumb screw mechani sm, to be disclosed in detail herein'after,'- includes a yoke which is secured to the waveguid raceam a threaded sleeve which is securdfto the platformsupporting the Shepard tube andfth octal socket. 3 Rotation of the thumb screw within the yoke 'provides adjustment of the vertical position of the complementarily threaded sleeve; and hence adjustment of the vertical position' of the Shepard tube and its output coaxial cahle 'iwith respect to the waveguide transmission system. 1 l i i 3 1 I Among theobjects of the invention are to provide an improved method of and means for coupling microwave energy into a waveguide transmissionsystem'l Another object of the invention is'to provide improved actuating mechanism for adjusting the elevation of a microwave generatorwith res'pect'to a waveguide transmission system whereby the penetration of a microwave radiator into a waveguide transmission system is varied'to controlthe microwave coupling thereto.

A further object of the invention is to provide an improved"micro-wave coupling device wherein a rack and pinion mechanism controls the penetration ofa' coaxial'cable type of microwave ra diator within a waveguide transmission system. An additional object of the invention is to provide an improved m'icro'wave coupling device wherein a thumb screw mechanism varies the penetration of a microwave radiator within a waveguide transmission system.

.The'invention will be further described by referen'certo the accompanying drawings of which Figure 1 'is'a cross-sectional view taken along the section line II of a first embodiment of the invention; Figure 2 is'a cross-sectional elevational view-taken allong'rthe'section line II'II of said cavity resonator having a frequency adjusting device 3, is inserted in a conventional octal type wafer socket, not shown, which is secured to a platform support 5 and held in position thereon by means of clamping devices I. The platform '5 includes vertical guide sleeves 9 slidably fitted to vertical cylindrical shafts II. The cylindrical shafts Ii are secured to the top face [3 of a rectangular waveguide transmission system and the top face l5 of an extension bracket I! which is secured to one of the side faces of the rectangular waveguide transmission system by means of screws 19. i v

The top face l3 of the waveguide transmission system includes a circular aperture 2| which is surrounded by the lower end of a short circular waveguide element 23. Theupper end of the circular waveguide element 23 includes cylindrical flexible contact elements 2 5. The contacts engage the outer conductor 21 of a coaxial output transmission line forming the output coupling means for the microwave generator at a region substantially an odd number of quarter wavelengths from said apertured waveguide face 13, as disclosed in the copending U. S. application of Vernon D. Landon, Serial No. 508,229, filed October 29, 1943, which describes tuning and coupling screws 'for waveguides. A portion of the inner conductor 29 of the coaxial transmission line from the microwave generator is exposed for a length of the order of wavelength at theoperating frequency. This portion of the coaxial line is given rigidity by enclosing the inner conductor in a cylindrical sleeve 3| of polystyrene or other low loss microwave insulation.

Vertically disposed racks 33, 3-5, secured to the vertically disposed sleeves 5, engage pinions 31, 3-9 respectively, which are secured to a control shaft 4|. The control shaft 4| is journalled in bearings 43, 45 secured to the rectangular waveguide and the supporting bracket H in any convenient manner. Acontrol knob 41, secured to the external end of the control shaft 41 provides rotational adjustment of the pinions 31, 39 and hence vertical adjustment through the racks 33, 35, respectively, of the platform 5 and microwave generator -I, and hence controls the penetration of the exposed quarter wave portion of the coaxial cable within the short circular waveguide 23 and the rectangular waveguide transmission system. As the platform 5 and microwave generator l are moved away from the waveguide transmission system, the penetration of the exposed inner conductor 29 of the coaxial cable within the circular and rectangular waveguides is decreased, thereby decreasing the microwave coupling between the generator and the waveguide transmission system.

Extremely loose coupling is provided when the inner conductor 29 is retracted entirely from the rectangular waveguide transmission system, since the constricted circular waveguide is operated well below cut-off.

Referring to Figures 3, 4, and 5, a thumb screw adjusting mechanism is substituted for the rack and pinion adjusting mechanism described in the device illustrated by Figures 1 and 2. A modification of the means for coupling the coaxial output transmission line from the Shepard tube microwave generator I through the aperture 2| in the rectangular waveguide faces 44 includes the flexible contacts 25 which engage the outer condu'ctor 21 of a coaxial line. The short section of circular waveguide 23 is omitted and a capacitive element, comprising a capacitor plate 49 and a mica dielectric element 5|, bypasses microwave energy to the rectangular waveguide faces l3 in the region of the aperture 2| in the rectangular waveguide face. This allows the cavity to be operated above ground potential. It should be understood however, that the construction employing the short section of round waveguide operated below cut-off, and described in the device of Figures 1 and 2, may be employed to equal advantage in the modifications of the invention illustrated in Figures 3, 4 and 5.

The platform 5 is secured to an elevator platform 53 by means of a double bracket 55. One end of an externally threaded cylindrical sleeve 51 is press-fitted into an aperture in the center of the elevator bracket 53 to support the threaded cylindrical sleeve '57 perpendicular with respect to the top face l3 of the rectangular waveguide transmission system.

.A forked yoke 59 is secured to the top face l3 of the waveguide transmission system by means of mounting screws 64. The ends of the forked yoke 59, remote from the mounting screws 61 are apertured to clear the threads'of the threaded cylindrical sleeve 51 and are separated to provide clearance for an internally threaded thumb screw B3. Rotation of the thumb screw 63 thereby provides elevatio'nal adjustment of the threaded sleeve 51 and hence the "elevator support 53, the support 5 and microwave generator l, and thereby varies the penetration of the exposed inner conductor 29 of the coaxial transmission line within the waveguide transmission system for varying the microwave coupling. A pair of guide sleeves 65, '67, which are press-fitted within apertures adjacent the ends of the elevator support 53, are slidably fitted to vertical pins '69, H respectively, for guiding the elevation al adjustment of the elevator support 53.

Thus the invention described comprises improved methods of and means for controlling the coupling of microwave energy from a microwave source 'to a waveguide transmission system wherein the microwave generator and the output coaxial coupling line projecting therefrom is mov able with respect to a waveguide transmission system to permit variationyof the penetration of the transmission line within the waveguide.

I claim as "my invent-ion:

1. Microwave coupling apparatus including a source of microwave energy, a concentric microwave transmission line connected to said source and including a microwave energy radiating element atits end remote from said source, a first waveguide for said 'ra-diated microwave energy, s'a'id waveguide having a wall apertured to receive said radiating element, a second waveguide having a critical cut-off frequency higher than said microwave source frequency, said second waveguide opening into 'said first waveguide through said aperture and extending 'coaxially with said concentric line, flexible contact means connecting the end of said second waveguide remote from said aperture to the outer conductor of said concentric line, and 'Ine'ans for simultaneously adjusting the relative positions of said source and said waveguides and the relative penetration of said radiating element within said waveguides for controlling the microwave coupling between said source and said first waveguide.

2. Microwave coupling apparatus including a source of microwave energy, a concentric micro- Wave transmission line connected to said source and including a microwave energy quarter wave radiating element at its end remote from said source, a first waveguide for said radiated microwave energy, said waveguide having a wall apertured to receive said radiating element, a second waveguide having a critical cut-01f frequency higher than said microwave source frequency, said second waveguide opening into said first waveguide through said aperture and extending coaxially with said concentric line, flexible contact means connecting the end of said second waveguide remote from said aperture to the outer conductor of said concentric line, and means for simultaneously adjusting the relative positions of said source and said waveguides and the relative penetration of said radiating element within said waveguides for controlling the microwave coupling between said source and said first waveguide.

3. Microwave coupling apparatus including a source of microwave energy, a concentric microwave transmission line connected to said source and including a microwave energy quarter wave radiating element at its end remote from said source, a first waveguide for said radiated microwave energy, said waveguide having a wall apertured to receive said radiating element, a second waveguide having a critical cut-ofi frequency higher than said microwave source frequency, said second waveguide opening into said first waveguide through said aperture and extending coaxially with said concentric line, flexible contact means connecting the end of said second waveguide remote from said aperture to the outer conductor of said concentric line at a point substantially a predetermined odd multiple of one quarter wavelength from said aperture, and means for simultaneously adjusting the relative positions of said source and said waveguides and the relative penetration of said radiating element within said waveguides for controlling the microwave coupling between said source and said first waveguide.

4. Microwave coupling apparatus including a source of microwave energy, a concentric microwave transmission line connected to said source and including a microwave energy radiating element at its end remote from said source, a first waveguide for said radiated microwave energy, said waveguide having a wall apertured to receive said radiating element, a second waveguide having a critical cut-off frequency higher than said microwave source frequency, said second waveguide opening into said first waveguide through said aperture and extending coaxially with said concentric line, flexible contact means connectin: the end of said second wave uide remote from Number said aperture to the outer conductor of said concentric line, and rack and pinion means for simultaneously adjusting the relative positions of said source and said waveguides and the relative penetration of said radiating element within said waveguides for controlling the microwave coupling between said source and said first waveguide.

5. Microwave coupling apparatus including a source of microwave energy, a concentric microwave transmission line connected to said source and including a microwave energy radiating element at its end remote from said source, a first waveguide for said radiated microwave energy, said waveguide having a wall apertured to receive said radiating element, a second waveguide having a critical cut-01f frequency higher than said microwave source frequency, said second waveguide opening into said first waveguide through said aperture and extending coaxially with said concentric line, flexible contact means connecting the end of said second waveguide remote from said aperture to the outer conductor of said concentric line, and rack and pinion means including cylindrical aligning means interposed between said source and said first waveguide for simultaneously adjusting the relative positions of said source and said waveguides and the relative penetration of said radiating element within said waveguides for controlling the microwave coupling between said source and said first waveguide.

6. Microwave coupling apparatus including a source of microwave energy comprising a thermionic tube oscillator, a concentric microwave transmission line connected to said source and including a microwave energy radiating element at its end remote from said source, a first waveguide for said radiated microwave energy, said waveguide having a wall apertured to receive said radiating element, a second waveguide having a critical cut-oil frequency higher than said microwave source frequency, said second waveguide opening into said first waveguide through said aperture and extending coaxially with said concentric line, flexible contact means connecting the end of said second waveguide remote from said aperture to the outer conductor of said concentric line, and rack and pinion means including cylindrical aligning means interposed between said source and said first waveguide for simultaneously adjusting the relative positions of said source and said waveguides and the relative penetration of said radiating element within said waveguides for controlling the microwave coupling between said source and said first waveuide.

HARRY KIHN.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Country Date 116,110 Australia Nov. 4, 1942 

